Oscillation
This presentation is the property of its rightful owner.
Sponsored Links
1 / 32

K2K near detector: PowerPoint PPT Presentation


  • 48 Views
  • Uploaded on
  • Presentation posted in: General

Oscillation maximum. Probability. dip. No oscillation. # of interactions. Oscillated. (ideal energy reconstruction). K2K near detector: Measurement of the n m flux in absence of oscillations and of the beam direction 3 different detectors:.

Download Presentation

K2K near detector:

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


K2k near detector

Oscillation

maximum

Probability

dip

No oscillation

# of interactions

Oscillated

(ideal energy reconstruction)

K2K near detector:

Measurement of the nmflux in absence of oscillations and of the beam direction

3 different detectors:

1 Kton Water Čerenkov:Small replica of Super-K; Fiducial mass 25ton.

Muon range detector:

MRD: Iron target 330 ton fiducial mass

Neutrino beam monitor:

Momentum and direction of muons

Scintillating fiber detector in water

(SciFi): fine grained water target CCQE identification Fiducial mass 6 ton.

SciBar

Since October 2003 the Lead Glass has been replaced with a scintillating bars 2.5x1.3x300 cm detector, 11 ton Fid.

Study of low energy neutrino interactions (osc. Max. @ 0.6 GeV)


K2k near detector

  • Events:

  • WC: only muon id.

  • SCIFI (water) 1 or 2 tracks, muon id.

  • SCIBAR (plastic scint.) 1 or 2 tracks, muon id.

  • For the events with 2 tracks make a classification in QE and

  • nQE just looking at the angle of the track wich is not the muon


K2k near detector

m–

Incomingnmdirection known

q

Proton undetectable

belowČerenkov threshold

Energy measurement of thenm in SuperKamiokandeusing the 1Rm sample under the hypothesis of the quasi-elastic scattering (dominant process at low energy):

nm + n m– + p

dE~60MeV

<10% measurement

Under the assumption that the initial neutron was at restthe kinematics of QE-CC can be used to find the energy of the incomingnm:

QE

inelastic

En (reconstructed) – En (true)


K2k near detector

For the events with 2 tracks make a classification in QE and

nQE just looking at the angle of the track wich is not the muon, should be within 25° from the expected proton direction

Scibar

For the 3 classes of events fit the muon variables data vs MC in bins of energy

Analysis based on the muon apart from the division in classes, no proton id, no measurement of prton energy


K2k near detector

WC

SCIFI

SCIBAR


K2k near detector

No significative differences SCIFI-SCIBAR, large difference in WC


K2k near detector

Formation Zone Intranuclear Cascade:

D.Autiero NUINT04

The formation length was introduced in analogy to the Landau Pomeranchuk effect to explain the suppression of the intranuclear cascade at high energies

The tracking of hadrons trhough the nucleus with known cross sections is performed only for hadrons formed inside the nucleus. Formation time in the rest frame of the hadron sampled from an exponential with average:

t0 is of the order of a few fm/c. In the lab frame

t=tSgs only low energy hadrons participate

Z. Phys C 43 (1989) 439

Z. Phys C 52 (1991) 643

The FZIC code performs a complete sampling of the nucleus in the impulse approximation assigning momenta and positions to the nucleons and then propagates the hadrons trough the nuclear medium developing the cascade

First application to neutrino interactions by Battistoni, Lipari, Ranft, Scapparone

hep-ph 9801426


K2k near detector

The NOMAD detector

Spectrometer: Dp/p = ±3.5% for p < 10 GeV/c

ECAL resolution:

WANF neutrino beam: <E>=24 GeV for nm

48 GeV for nm CC


K2k near detector

Nomad typical events:

nm + N m– + X

m– track

ne + N  e– + X

Energy depositions in the ECAL

ne + N  e+ + X


K2k near detector

1 fm/c

2 fm/c

5 fm/c

No INC

Proton and neutron yields increase with the INC

(DIS, Nomad beam and target, pure MC level):

Low momenta

Large angles

p

Momentum (GeV/c)

Angle wrt incoming neutrino (rad)

n

Look for the protons in order to tune the model

Momentum (GeV/c)

Angle wrt incoming neutrino (rad)


K2k near detector

Formation time tuning, after fragmentation tuning: INC improves the agreement data-MC, (minimum found at 2 fm/c)

No INC

2 fm/c

Charged hadrons multiplicity

Charged hadrons multiplicity

2 fm/c

No INC

Total event charge

Total event charge


K2k near detector

Hadrons spectra and angular distributions

No INC

2 fm/c

-

-

+

+

Hadrons momenta (GeV/c)

Hadrons momenta (GeV/c)

No INC

2 fm/c

-

+

-

+

Hadrons angular dist. (rad)

Hadrons angular dist. (rad)


K2k near detector

Looking for the presence of the protons from INC ….

Hadron with the largest angle (wrt incoming neutrino) in the event

No INC

2 fm/c

Negatives

Negatives

Hadron with largest angle (rad)

Hadron with largest angle (rad)

No INC

2 fm/c

Strong improvement of the agreement data-MC for the positives due to the INC protons

Positives

Positives

Hadron with largest angle (rad)

Hadron with largest angle (rad)


K2k near detector

Looking for the presence of the protons from INC ….

Spectra for hadrons with 0.5<q<1.57

No INC

2 fm/c

Negatives

Negatives

Momentum (GeV/c)

Momentum (GeV/c)

No INC

2 fm/c

Positives

Positives

p

p

p

p

Momentum (GeV/c)

Momentum (GeV/c)


K2k near detector

Backward protons (kinematically forbidden for neutrino interactions on stationary nucleons) are a very sensitive observable for the tuning of INC

Nomad has published a paper on the production of backward particles: P.Astier et al. Nuc. Phys. B 609 (2001), see also M. Veltri Nuint01 proc.

Protons can be identified by range looking in the sample of backward stopping particles

Invariant cross section:

# of BP per DIS nm CC


K2k near detector

NEG-N: invariant spectrum in NOMAD for various formation times

The slope is not affected by the formation time, the rate is quite sensitive to the formation time

The formation time tuned on the hadronic distributions predicts the correct rate of BP.

On the contrary one can constrain the formation time from the measurement of BP which gives: 2 +0.9–0.5 fm/c


K2k near detector

Ar

Pi0 momentum spectrum

O/C

GeV/c


K2k near detector

50000 events /run Resonances Rein & Seghal model

Particles in the final state:

Ar vs O +3% Pi0 with a softer spectrum (-9%)

Ar vs O +17% protons


K2k near detector

Upper limit, neglecting completely nuclear effects (19%)


K2k near detector

Upper limit II, fitting the invariant mass of the NEUT events with NUX (no nuclear effects)  18% discrepancy


K2k near detector

When adding protons and detector mass isn’t enough…

D. Harris, proton driver review

For any of these experiments, detectors see different mixes of events between near and far. Cross section uncertainties don’t all cancel!

Looking for differences between n and anti-n probabilities of at most 15-20%…need to measure probabilities to 5% or better for a 3s determination!

Problem: no cross sections at these

energies are known any better than

about 20%...

Minerna will provide precise n measurements, but we still need anti-n cross sections…

NOvA pre-PD rates


K2k near detector

Some remarks:

1) The LAr detector will be the ideal detector to study the nuclear effects and accurately model the MC on Ar (MC validator):

Capability to measure exclusive states

Particle id (ionization)

Energy measurement

Homogeneus and hermetic detector, reconstruction systematics reduced

2) The ice target will allow to measure also the interactions on oxigen (on a subsample of the phase space) and cross-check the model

3) The WC detector will allow to correlate accurately the (beam*interaction model) data obtained in the LAr with the WC reconstruction, these beam data will be extrapolated to the far detector


K2k near detector

  • A full systematic analysis has not been completed at the moment neither for the 280m nor for the 2Km LAr+WC (using assumption like 10% syst…)

  • b) WC alone vs SK is nevertheless based on some MC+flux assumptions, what if in reality they are wrong ? We need absolutely the LAr to cross-check the flux*interaction model

  • c) In real life it may take many years before reaching a good understanding of the systematics (e.g. NOMAD numu  nue analysis ~ 5 years)

  • d) The WC detector has never been used at this level of precision, we absolutely need all the handles for the systematics, the LAr will be precious


K2k near detector

Real QE events in the 50l

LAr chamber exposed at WANF


  • Login